Sugimoto T, Kano J, Fukase M, Fujita T
Department of Medicine, Kobe University School of Medicine, Japan.
J Cell Physiol. 1992 Jul;152(1):28-34. doi: 10.1002/jcp.1041520105.
The present study was performed to investigate the regulation of cytosolic pH (pHi) and DNA synthesis by parathyroid hormone(PTH) and PTH-related peptide (PTHrP) in osteoblasts, using osteoblastic osteosarcoma cells, UMR-106 which possessed PTH-responsive dual signal transduction systems (cAMP-dependent protein kinase (PKA) and calcium/protein kinase C [Ca/PKC]) and amiloride-inhibitable Na+/H+ exchange system. Both human (h)PTH-(1-34) and hPTHrP-(1-34) caused a progressive decrease in pHi and the inhibition of [3H]thymidine incorporation (TdR) to the same degree in a dose-dependent manner with a minimal effective dose of 10(-10) M. Dibutyryl cAMP (10(-4) M and Sp-cAMPS (10(-4) M), a direct stimulator of PKA also caused a progressive decrease in pHi, and calcium ionophores (A23187 and ionomycin, 10(-6) M) caused a transient decrease in pHi. Pretreatment with amiloride (0.3 mM) mostly blocked dbcAMP- and Sp-cAMPS-induced decrease in pHi but did not affect calcium ionophore-induced decrease in pHi. In the presence of amiloride, PTH and PTHrP caused a transient decrease in pHi, which was similar to the pattern of calcium ionophore-induced change in pHi. Amiloride did not affect the inhibition of TdR by PTH or PTHrP as well as that by cAMP analogues or calcium ionophores. The present study indicated that PTH and PTHrP caused cytosolic acidification through PKA-inhibited Na+/H+ exchange and increased cytosolic calcium-induced pathway and that the regulation of DNA synthesis by PTH and PTHrP was not via Na+/H+ exchange system.
本研究旨在利用成骨细胞性骨肉瘤细胞系UMR-106（其具有甲状旁腺激素（PTH）反应性双信号转导系统（环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）和钙/蛋白激酶C [Ca/PKC]）以及氨氯吡咪抑制性Na⁺/H⁺交换系统），研究PTH和PTH相关肽（PTHrP）对成骨细胞胞质pH（pHi）和DNA合成的调节作用。人（h）PTH-（1-34）和hPTHrP-（1-34）均以剂量依赖性方式使pHi逐渐降低，并同等程度地抑制[³H]胸腺嘧啶核苷掺入（TdR），最小有效剂量为10⁻¹⁰ M。二丁酰cAMP（10⁻⁴ M）和Sp-cAMPS（10⁻⁴ M），PKA的直接刺激剂，也使pHi逐渐降低，钙离子载体（A23187和离子霉素，10⁻⁶ M）使pHi短暂降低。用氨氯吡咪（0.3 mM）预处理大多可阻断二丁酰cAMP和Sp-cAMPS诱导的pHi降低，但不影响钙离子载体诱导的pHi降低。在氨氯吡咪存在的情况下，PTH和PTHrP使pHi短暂降低，这与钙离子载体诱导的pHi变化模式相似。氨氯吡咪不影响PTH或PTHrP以及cAMP类似物或钙离子载体对TdR的抑制作用。本研究表明，PTH和PTHrP通过PKA抑制的Na⁺/H⁺交换和增加的胞质钙诱导途径导致胞质酸化，且PTH和PTHrP对DNA合成的调节并非通过Na⁺/H⁺交换系统。
